Modular fuel-cell stack assembly

ABSTRACT

A modular multi-stack fuel-cell assembly in which the fuel-cell stacks are situated within a containment structure and in which a gas distributor is provided in the structure and distributes received fuel and oxidant gases to the stacks and receives exhausted fuel and oxidant gas from the stacks so as to realize a desired gas flow distribution and gas pressure differential through the stacks. The gas distributor is centrally and symmetrically arranged relative to the stacks so that it itself promotes realization of the desired gas flow distribution and pressure differential.

BACKGROUND OF THE INVENTION

This invention relates to fuel cell systems and, more particularly, tomulti-stack fuel cell systems.

In building fuel-cell systems, the fuel cells are conventionally stackedone on the other to form a fuel-cell stack. The number of cellsdetermines the power rating of the stack and to provide systems withhigher power ratings, a number of fuel-cell stacks are utilized and theoutputs of the fuel cell stacks combined to provide the desired poweroutput.

In one type of multi-stack-fuel cell system, it has been proposed tomodularize the system by forming modular multi-stack fuel cellassemblies each of which contains a plurality of fuel-cell stacks housedwithin an enclosure. In a system of this design developed for hightemperature fuel cell stacks and, in particular, for carbonate fuel cellstacks, a rectangular or box-like containment structure is employed asthe enclosure and the stacks are arranged in line along the length ofthe structure. Each of the stacks within the structure has inletmanifolds for receiving the fuel and oxidant gas needed to operate thestack and outlet manifolds for outputting exhaust fuel and oxidant gasesfrom the stack.

The containment structure includes fuel and oxidant gas inlet ports forcommunicating through piping or conduits with the respective fuel andoxidant gas inlet manifolds of the stacks. The structure also has fueland oxidant gas outlet ports for communicating through piping with theoxidant and fuel gas outlet manifolds. The fuel inlet ports are arrangedin line along the length of the structure and a header delivers the fuelto each of the ports. A similar type of arrangement is used for theoxidant gas inlet ports. The fuel and oxidant gas outlet ports alsocommunicate with respective headers for carrying the exhaust gases fromthe modular assembly.

In order to insure an appropriate uniform flow distribution and adesired pressure differential through the stacks, flow baffles areprovided in the piping or conduits connecting the fuel and oxidant gasinlet ports to the respective stack inlet manifolds. Each of the stacksand the piping within the enclosure are also insulated to thermallyisolate the stacks from the containment structure.

The cold box-like design of the container structure requires thermalexpansion joints inside as well as outside of the containment structureto minimize the pressure differential across the fuel and oxidant seals.Nitrogen is also provided to purge any minute leaks from the fuel cellstacks into the enclosure.

While modular multi-stack fuel cell assemblies of the above typeperformed as desired, the piping and baffle requirements made eachassembly complex and expensive. The thermal insulation requirements werealso stringent, further adding to the cost of each assembly.Additionally, the need for a nitrogen gas purge added another gas streamincreasing the process control requirements. These factors have leaddesigners to look for less complex and less costly design alternatives.

It is, therefore, an object of the present invention to provide animproved modular multi-stack fuel-cell assembly.

It is a further object of the present invention to provide a modularmulti-stack fuel-cell assembly in which stack to stack flow distributionand differential pressure requirements are realized in a simpler andmore cost effective manner.

It is yet another object of the present invention to provide a modularmulti-stack fuel cell assembly in which input and output portrequirements and piping requirements are significantly reduced.

It is a further object of the present invention to provide a modularmulti-stack fuel cell assembly in which the manner of insulating theassembly is improved.

It is a further object of the present invention to provide a modularmulti-stack fuel cell assembly in which the enclosure of the assemblyand the connections to and from the enclosure are simplified.

It is yet an additional object of the present invention to provide amodular multi-stack fuel cell assembly of the above type whicheliminates the use of a nitrogen purge, minimizes the thermal insulationand reduces the piping and associated expansion joints.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention the above andother is objectives are realized in a modular multi-stack fuel cellassembly in which the fuel cell stacks are situated within a containmentstructure and in which a gas distributor is provided in the structureand distributes received fuel and oxidant gases to the stacks andreceives exhausted fuel gas from the stacks so as to realize a desiredgas flow distribution and gas pressure differential through the stacks.Preferably, the gas distributor is centrally and symmetrically arrangedrelative to the stacks so that it itself promotes realization of thedesired uniform gas flow distribution and low pressure differential.

In further aspects of the invention, the containment structure acts asthe oxidant gas input manifold for the stacks and the end plates of eachstack act to couple fuel to and exhausted fuel and oxidant gas from thestacks. Additional aspects of the invention include thermally insulatingthe assembly on portions of the inner surfaces of the containmentstructure so as to alleviate the need to insulate the stacks and flowdistribution piping, forming the containment structure from an upperenclosure which surrounds the stacks and a base member engaged by theupper enclosure and supporting the stacks, use of single ports for eachof the inlet and outlet fuel and oxidant gas ports and configuring eachof these ports with an outer wall having stepped transitions.

In the embodiment of the invention to be disclosed hereinbelow, theupper enclosure includes a head which is preferably torispherical and abody extending from the head, which is preferably a round or oval shapedpressurized vessel. The base member, in turn, includes a base platewhich houses a base frame which supports the fuel cell stacks which arefour in number and situated so as to have two sets of opposing stacks.This permits the gas distributor to be located centrally of the stacksand to be symmetrically configured relative to the stacks. Each of thestacks has manifolds on three faces, one inlet manifold for fuel gas andthe two outlet manifolds for exhausted fuel gas and exhausted oxidantgas, respectively. The upper enclosure itself acts as the oxidant gasinlet manifold for a fourth face of each stack.

The gas distributor has three successive sections. One section receivesfuel and distributes it to piping coupled to a first end plate of eachstack. The others receive exhausted oxidant gas and exhausted fuel gasvia piping coupled to a second end plate and the first end plate,respectively, of each stack.

The insulation for the containment structure is provided on the upperenclosure inner wall and comprises a plurality of layers. Each layer ofinsulation is segmented into abutting sections. The positions at whichthe segments abut are offset from layer to layer. A clip and pinarrangement is used to secure the layers together and to the inner wallof the enclosure. A thin sheet metal liner is used on the insulation toprevent direct contact with the oxidant gas.

The stepped inlet and outlet fuel and oxidant gas ports in the enclosurewall are arranged in a line on one side of the enclosure for compactnessand ease of installation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and aspects of the present invention willbecome more apparent upon reading the following detailed description inconjunction with the accompanying drawings, in which:

FIG. 1 shows a modular multi-stack fuel cell assembly and gas flowdistributor in accordance with the principles of the present inventionwith the upper enclosure of the containment structure in place;

FIG. 2 shows the modular multi-stack fuel cell assembly of FIG. 1 withthe upper containment structure removed;

FIG. 3 shows a top view of the assembly of FIG. 1 with the upperenclosure of the containment vessel removed;

FIG. 4 shows a cross-section view of the containment structure of theassembly of FIG. 1;

FIG. 5 shows a top view of the lower support base members for thecontainment structure of fuel cell assembly FIG. 1;

FIG. 6 shows an isometric cross-section of the containment structure ofthe assembly of FIG. 1;

FIG. 7 shows an elevation view of the gas flow distributor of FIG. 1;

FIGS. 8-10 show various plane views of the fuel cell assembly and gasflow distributor of FIG. 1;

FIG. 11 illustrates an isometric view of the gas flow distributor withthe exhaust oxidant gas internal baffle being shown;

FIG. 12 shows a conventional fuel cell stack assembly with solid endplates;

FIGS. 13, 14 and 15A-15D show the a stack of the fuel cell assembly ofFIG. 1 depicting the details of the hollow, flow through end plates ofthe stack; and

FIGS. 16-19 show the details of the thermal insulation used in thecontainment structure of the fuel cell assembly of FIG. 1.

DETAILED DESCRIPTION

FIGS. 1-11 show various views of a modular multi-stack fuel cellassembly 1 in accordance with the principles of the present invention.The assembly 1 includes a plurality of like fuel cell stacks, shown asopposing stacks 2 and 3 and opposing stacks 4 and 5. To permit viewingof the other components of the assembly 1, the stacks 2 and 5 are notdepicted in FIG. 2, but can be seen FIG. 3 and FIGS. 8-10.

The stacks 2-5 each extend height-wise in the vertical direction and aresupported on a base section 7 of a containment structure 6. Thecontainment structure also includes an upper enclosure 8 (shown inFIG. 1) which surrounds and encloses the fuel cell stacks. Centrallysituated relative to the stacks in the enclosure 8 is a gas flowdistributor 9 which serves as the unit for the distribution of fuel andoxidant to and from the fuel cell stacks.

More particularly, referring to FIG. 2, the distributor 9 includes anoxidant exhaust gas section 11, a fuel inlet section 12, and a fuelexhaust gas section 13, all aligned in the vertical direction.Additionally, the distributor 9 includes piping or conduits for couplingthe respective fuel or oxidant constituents to and from the distributorsections. Specifically, as shown in FIGS. 2 and 8, conduits 14, 15, 16and 17, couple exhaust oxidant gases from the respective stacks 2, 4, 3and 5 to the oxidant exhaust gas section 11. Conduits 18, 19, 21 and 22,in turn, couple fuel from the fuel inlet section 12 to the stacks 4, 5,3 and 2, respectively, as shown in FIG. 9, and conduits 23, 24, 25 and26 couple exhaust fuel gases from the stacks 4, 5, 3 and 2,respectively, to the fuel exhaust section 13, as shown in FIG. 10.

The distributor also includes further conduits 27, 28 and 29, as shownin FIGS. 2 and 7. Referring to the latter two figures and FIG. 1, theconduit 27, which carries oxidant exhaust gases from the section 11,connects to an oxidant gas exhaust port 31 in the upper enclosure 8. Theconduit 28, which receives fuel from a fuel inlet port 32 in the upperenclosure 8, connects to the section 12. The conduit 29, in turn, whichcarries fuel exhaust gas from the section 13, connects to the fuel gasexhaust port 33 in the upper enclosure.

In the case shown, each of the fuel cells stacks 2-5 is a hightemperature fuel cell stack, as, for example, a molten carbonate fuelcell stack.

In accord with the invention, the distributor 9, including the sections11-13 and the conduits 18, 19 and 21-29, is adapted to itself promotedesired uniform gas flow and desired uniform pressure differentialthrough the stacks 2-5. In the case shown, this is accomplished bydisposition of the distributor 9 symmetrically and centrally of thestacks.

Specifically, the fuel inlet conduit 28 and fuel distribution section 12are used in common for all the stacks, and equal length conduits 18, 19,21 and 22, are used for carrying fuel from the distribution section 12to the respective stacks. Similarly, equal length conduits 14-17 coupleexhaust oxidant gas from the stacks to a common oxidant exhaustdistribution section 11 from which the gas exits through a commonconduit 27. Likewise, equal length conduits 23-26 carry the fuel exhaustgas from the stacks to the common fuel exhaust distribution section 13from which this gas exits through the common conduit 29.

In order to assure uniform oxidant gas flow and pressure drop to thefuel cell stacks 2-5, the exhaust distributor section 11 is fittedinternally with a continuing section 10 of the conduit 27, as shown inFIG. 11. As shown, the continuing section is a part cylindrical shape,and in particular, a one half cylinder.

Thus, with this configuration for the distributor 9, both the flowdistribution of the fuel and the flow distribution of the oxidant ismade more uniform. The pressure differential of the gases through thestacks is also made more uniform. The need for additional components toprovide this uniformity is, therefore, significantly reduced through theuse of the distributor 9. The overall energy losses associated with theflow distribution are also minimized.

Also contributing to the uniformity in the flow distribution of theoxidant and fuel is the end plate assemblies of the fuel cell stacks2-5. These end plate assemblies incorporate a hollow flow through designwhich differs form the solid end plate design of convention fuel cellstacks. More particularly, FIG. 12 shows a conventional fuel cell stack120 with solid upper and lower end plates 121 and 122. A manifold 123couples supply gas to the fuel cells 120A of the stack 120 and amanifold 124 couples exhaust gas from the fuel cells. A compressionassembly 125 having upper and lower compression plates 125A maintainsthe cells of the stack in place. Upper and lower terminals 126 and 127extending through the compression plates and connecting to the endplates permit coupling of electrical energy from the stack.

The conventional stack 120 of FIG. 12 is not able to provide uniformflow due to the asymmetric manifold connections which result, in part,from the solid end plates. The stack 120 also requires additionalelectric heaters due to these end plates.

In contrast, each of the fuel cell stacks 2-5 of the invention includesupper and lower end plate assemblies 601 and 701. FIGS. 13, 14 and15A-15D show these assemblies for the stack 2. The stacks 3-5, which areof the same configuration as the stack 2, have like end plateassemblies. As will be discussed below, the end plate assemblies 601 and701 allow fuel to be readily coupled to the stacks by the equal lengthconduits 18, 19, 21 and 22, and further permit exhausted oxidant gas andexhausted fuel gas to be likewise readily coupled from the stacks viathe equal length conduits 14-17 and equal length conduits 23-26,respectively.

Referring to FIGS. 13 and 14, the stack 2 has opposing first and secondfaces 101 and 102 associated with oxidant gas flow and opposing thirdand fourth faces 103 and 104 associated with fuel gas flow. The stack 2further has first, second and third manifolds 202, 203 and 204 whichabut the stack faces 102, 103, and 104, respectively. Retentionassemblies (not shown) maintain these manifolds against the stack facesand a compression assembly 401 having compression plates 402 compressthe upper and lower end plates 601 and 701 to maintain the cells 2A ofthe stack in place. Upper and lower terminals 501 and 502 extendingthrough the compression plates 402 permit obtaining electrical outputfrom the stack.

FIGS. 15A-15B show further details of the upper end plate assembly 601.As shown, the end plate assembly 601 has inlet areas 603 on a face 602of the assembly. This face of the assembly is overlapped by and receivesexhausted oxidant gas from the respective oxidant exhaust gas outletmanifold 202 of the respective stack. The end plate assembly 601 furtherincludes or defines a passage 604 which extends through the assembly toan outlet area 606. The outlet area 606 is disposed on another face 605of the assembly, the latter face, in the case shown, opposing the face602 of the assembly. The outlet area 606, in turn, couples with theconduit 14 of the distributor 9 carrying oxidant gas from the respectivestack. The edges of the end face 602 of the assembly 601 form seal areaswhich accommodate the seals of the manifold 202. If desired, these sealareas can be extended using a recessed geometry to further accommodatethe dimensional changes occurring during long term operation.

Also, in the case shown, posts 607 are distributed in the interior ofthe end plate assembly 601 and extend between upper and lower faces 608and 609 of the assembly. The posts 607 provide mechanical strength tothe end plate assembly and electrical contact between the faces 608 and609. The end plate assembly thus provides electrical contact between thestack terminal 501, affixed to the face 608 of the assembly, and thecells of the stack which are in electrical contact with the face 609 ofthe assembly.

In the form of the end plate assembly 601 shown in FIGS. 13 and 15A-15B,the assembly is configured as a hollow body, shown as a hollowrectangular body. The faces 602 and 605 are, in turn, defined byopposing side walls of the body, the passage 604 by the interior spaceof the body, and the faces 608 and 609 by the opposing upper and lowerwalls of the body.

The overall thermal mass of the end plate assembly 601 is reduced due tothe hollow configuration. The flow through geometry of the assemblyallows the process gases to provide heat for the assembly, and thuseliminates the need for a separate electric heater and associatedparasitic power. The resultant end plate assembly is much closer inthermal response to the rest of the fuel cell stack. The overall weightand cost are reduced, while the net electrical output available from thefuel cell stack is increased.

Lower end plate assembly 701 is shown in detail in FIGS. 14 and 15C-1SD. As shown, this end plate assembly has a first face 702 whichincludes an inlet area 703 adapted to be coupled to the conduit of thedistributor 9 delivering fuel to the respective stack. This face alsoincludes an outlet area 704 which is adapted to be coupled to theconduit of the distributor 9 carrying exhausted fuel gas from the stack.The end plate assembly 701 further defines a first passage 705 whichcouples with the inlet area 703 and carries fuel delivered to the inletarea to a second face 706. This face of the end plate assembly isoverlapped by the fuel inlet manifold of the respective stack. A thirdface 707 of the plate assembly having inlet area 708 is overlapped bythe fuel exhaust gas outlet manifold of the stack. The end plateassembly 701 additionally defines a further passage 709 which couplesthe inlet area 708 to the outlet area 704.

The end plate assembly 701 also includes in its interior posts 711connected between the opposing faces 712 and 713 of the plate assembly.These posts, like the posts 607 of the end plate assembly 601, providemechanical strength to the assembly and electrical contact between thefaces 712 and 713. This contact, in turn, provides electrical contact tothe stack terminal 502 affixed to the face 713.

In the case shown in FIGS. 15C-15D, the end plate assembly 701 is alsoin the form of a hollow body and, in particular, a rectangular hollowbody. The face 702 is defined by a first side wall of the hollow body,the faces 706 and 707 by opposing second and third side walls of thebody, the passage 705, by a tube extending through the interior of thebody, the passage 709 by the interior of the body, and the surfaces 712and 713 by the opposing upper and lower walls of the body.

As can be appreciated and as discussed hereinabove, with the end plateassemblies 601 and 701 of each stack configured in the above manner,oxidant and fuel are coupled to and from the stacks exclusively throughthe end plate assemblies. The flow connection can be from the sidefaces, top or bottom faces. The flow of oxidant and fuel through thestack 2 will be described with reference to FIGS. 13 and 14. The flowthrough the other stacks is similar.

Specifically, oxidant gas entering the upper enclosure 8 through theoxidant gas inlet port 34 is conveyed by the upper enclosure acting asan oxidant gas inlet manifold to the face 101 of the stack 2. This facehas inlets for the oxidant flow channels of the fuel cells 2A of thestack. The oxidant then flows through these channels of the fuel cellsand oxidant exhaust gas exits these channels at the opposing face 102 ofthe stack 2. The manifold 202 abutting this stack face then carries theoxidant exhaust gas to the face 602 having the inlet areas 603 of theend plate assembly 601. The oxidant exhaust gas is then conveyed by thepassage 604 through the assembly to the outlet area 606. This area iscoupled to the conduit 14 of the distributor 9 (see, FIG. 8) whichconduit carries the gas to the oxidant exhaust gas section 11 of thedistributor. The oxidant exhaust gas then leaves the section 11 via theconduit 27 and exits the upper enclosure though the outlet port 31.

The fuel, on the other hand, enters the upper enclosure via the fuelinlet port 32 and is coupled to the distributor section 12 via theconduit 28 (see, FIG. 9). The distributor section 12 passes the fuel tothe conduit 22 which is coupled to the inlet area 703 of the lower endplate assembly 701 (see, FIG. 14). The fuel passes from the inlet areathrough the passage 705 which deposits the fuel in the fuel gas inletmanifold 203. The fuel then passes through the fuel cells 2A of thestack 2 and fuel exhaust gas enters the fuel gas outlet manifold 204.This manifold couples the fuel exhaust gas to the face 707 having theinlet area 708 of the plate assembly 701. The fuel exhaust gas passesfrom the inlet area 708 through the passage 709 of the plate assemblyarriving at the outlet area 704.

The gas exits the outlet area 704 into the conduit 26 of the distributor9 (see, FIG. 10) and is carried to the fuel exhaust gas section 13 ofthe distributor. The exhaust gas leaves this section through the conduit29 and exits the enclosure through the exhaust gas outlet port 33.

As can be appreciated, with the end plate assemblies 601 and 701, thegas flow connections to the stacks 2-5 are made only at the end platesassemblies and no connections are made at the manifolds. Thisarrangement mechanically decouples the manifolds from the stack leadingto a better mechanical design for long term operation. Also, themechanical connections to the stronger end plates are more robust thanthose conventionally made to the thin-walled stack manifolds.

FIGS. 4 and 6 show elevation and cross-sectional views, respectively, ofthe containment structure 6 of the modular multi-stack fuel cellassembly of FIG. 1. As above-indicated, the containment structure 6includes a base section 7 which supports an upper enclosure 8.

In the case shown, the upper enclosure 8 has a cylindrical shell orvessel body 8A and a torispherical cover or top 8B. This permits the useof a thin structure for the cover 8B, while still being able toaccommodate the pressurized environment of the upper enclosure.Alternately, the cover 8B may be formed to have a flat configuration toaccommodate a greater height of the stack and to realize a more compactlayout.

Situated along a common vertical line on the vessel body 8A are theoxidant gas inlet port 34, the oxidant exhaust gas outlet port 31, thefuel inlet port 32 and the fuel exhaust gas outlet port 33. As can beseen in the views of FIGS. 4 and 6, the ports 31-34 are each in the formof a nozzle with stepped transitions. Thus the port 34 has steptransitions 34A, the port 31, stepped transitions 31A, and the ports 32and 33, stepped transitions 32A and 33A. These transitions allow therespective nozzles to accommodate expansion of the vessel body 8A, whilestill maintaining an effective connection to the piping connected to thenozzles. This avoids the need to use bellows or other types of expansionjoints to maintain these connections, thereby conserving space andlessening costs. The stepped transitions also help in thermallyinsulating the nozzles as discussed below.

More particularly, the volume of the regions defined by the steppedtransitions can be filled with layers of cylindrical thermal insulation,as indicated in FIG. 4. This is seen in greater detail in FIG. 19 whichshows in enlarged scale the nozzle 34 with the stepped transitions 34A.As can be seen, cylindrical insulation layers 901, 902 and 903 fill thevolume of the regions defined by the stepped transitions 34A. The pipingwhich is coupled through the nozzle can thus be thermally insulated fromthe surfaces of the vessel body 8A so as to maintain the outer surfaceof the vessel body at a much lower temperature than the interior spacedefined by the upper enclosure.

As seen in detail in FIG. 5, the bottom section 7 of the containmentstructure 6 comprises a vessel support ring 41 and a structural base 42.The ring 41 is made from structural steel to which the vessel body 8Aand the structural base 42 are attached, respectively. The structuralbase 42 comprises stack support beams 43 and 44. The beams are arrangedin a grill pattern, with groups of four beams 44 forming a rectangularsupport frame 45 for each of the stacks 2-5. The beams 43, in turn, arearranged to cross each other and to support the gas distributor 9 attheir area of intersection. The beams 43 also intersect the innercorners of the rectangular support frames. The beams 43 are adapted tobe mounted to the floor of the facility in which the assembly 1 is to beused and provide the major structural support for the assembly.

Referring to FIG. 16, in order to thermally insulate the area 41A withinthe ring 41 below the vessel body 8A from the heat generated within thevessel body 8 by the stacks 2-5, the bottom section 7 further includes athermally insulated floor 46 (see FIG. 16) which covers the opening andis also supported by the ring 41. The floor has openings for passage oflower ends of the stacks 2-5 therethrough so that the compression plateof each stack can rest on the beams 44 of the corresponding supportframe 45. The space below the thermal insulation 46 can thus be used tohouse components of the compression assemblies of the stacks.Additionally, all electrical components to be used with the stacks canbe housed in this thermally insulated area as well as all otherpenetrations into the assembly 1, such as, for example, electricalpenetrations. The floor 46 also has drains for passage of collectedwater from internal condensation.

In addition to insulating the area 41A of the bottom section 7 from theheat within the upper enclosure 8, the vessel body 8A and the top cover8B are each thermally insulated so that the outer surface of the upperenclosure is also thermally insulated from the heat within theenclosure. More particularly, the inner walls of the vessel body and topcover are provided with like thermal insulation assemblies 47 and 48 asshown in FIGS. 4, 17, 17A, 18 and 19.

As can be seen, the assemblies 47 and 48 each comprise a condensationaccumulation layer 49 formed of fine mesh stainless steel. This layerabuts the inner wall of the enclosure and accumulates any moisture onthe wall, allowing the moisture to condense and drip down to be purgedfrom the interior of the enclosure. A next layer 50 of hydrophobicmaterial such as micro-porous silica follows layer 49. Thermalinsulation layers 51 then follow the layer 50 and a stainless steellining 52 follows the insulation layers 51.

As shown in FIG. 17A, the thermal insulation layers 51 each comprisethermal insulation segments 51A which are abutted against each other toform the layer. The segments of successive layers are furthermorestaggered or off-set from each other. As seen in FIGS. 18 and 19, pins53 are passed through the layers of the assemblies 47 and 48 and areattached as by welding to the inner surface of the enclosure. Clips 54are used to secure the segments 47 and 48 to the pins 53. While a clip54 can be provided to secure each segment of a layer to a pin, todecrease the amount of heat loss carried by the pin clip configuration,the number of pins can be decreased by allowing a segment in a layer tobe secured by an overlapping clipped segment of an outer layer.

With the assemblies 47 and 48 configured as above-described, the heatgenerated in the upper enclosure 8 is prevented from reaching the outersurface of the enclosure. Thus temperatures of approximately 1200° F. inthe interior of the enclosure, which are typical temperatures where thefuel stacks 2-5 are molten carbonate fuel stacks, can be reduced toapproximately 100° F. at the outer wall of the enclosure.

Maintenance of the outer surface of the upper enclosure at this lowertemperature is also facilitated by the thermally insulated steppedtransitions of the nozzles in the upper enclosure as previouslydiscussed and shown in FIG. 19. This insulation insulates the pipingcarrying hot oxidant and fuel to and from the enclosure from the beingaffected by the hot gases, thereby maintaining the outer surfacetemperature of the enclosure at the lower temperatures.

In all cases it is understood that the above-described arrangements aremerely illustrative of the many possible specific embodiments whichrepresent applications of the present invention. Numerous and variedother arrangements can be readily devised in accordance with theprinciples of the present invention without departing from the spiritand scope of the invention.

1. A modular multi-stack fuel cell assembly comprising: a plurality offuel cell stacks; and a gas distributor disposed centrally of said fuelcell stacks, said gas distributor distributing received fuel to each ofsaid fuel cell stacks and receiving exhausted fuel gas and exhaustedoxidant gas from each of said fuel cell stacks.
 2. A modular multi-stackfuel cell assembly in accordance with claim 1 in which: said gasdistributor is disposed symmetrically with respect to said fuel cellstacks.
 3. A modular multi-stack fuel cell assembly in accordance withclaim 2 in which: said gas distributor includes first, second and thirdsections, said first section for distributing received fuel to each ofsaid fuel cell stacks, said second section for receiving exhausted fuelgas from each of said fuel cell stacks and said third section forreceiving exhausted oxidant gas from each of said fuel cell stacks.
 4. Amodular multi-stack fuel cell assembly in accordance with claim 3, inwhich: said gas distributor further includes: first piping of the samefirst predetermined length from said first section of said gasdistributor to each of said multi-stack fuel cell assemblies; secondpiping of the same second predetermined length from said second sectionof said gas distributor to each of said multi-stack fuel cellassemblies; and third piping of the same third predetermined length fromsaid third section of said gas distributor to each of said multi-stackfuel cell assemblies.
 5. A modular multi-stack fuel cell assembly inaccordance with claim 4, in which: said modular multi-stack fuel cellassembly further includes a containment structure; and said gasdistributor further includes: a first conduit from said first section toan oxidant gas outlet port of said containment structure; a secondconduit from said second section to an fuel gas outlet port of saidcontainment structure; and a third conduit from said third section to afuel gas inlet port of said containment structure.
 6. A modularmulti-stack fuel cell assembly in accordance with claim 5, in which:said first, second and third sections of said gas distributor arealigned vertically; said oxidant gas outlet port, said fuel gas outletport and said fuel gas inlet port are aligned vertically; and saidfirst, second and third conduits are aligned vertically.
 7. A modularmulti-stacl fuel-cell assembly in accordance with claim 5, in which:said first conduit has a portion extending into said first section.
 8. Amodular multi-stack fuel cell assembly, in accordance with claim 7, inwhich: said portion of said first conduit has a part cylindrical shape.9. A modular multi-stack fuel cell assembly in accordance with claim 1,further comprising: a containment structure enclosing said fuel cellstacks, said containment structure having a base section supporting thefuel cell stacks in predetermined positions and an enclosure engagingthe base member and enclosing the fuel cell stacks.
 10. A modularmulti-stack fuel cell assembly in accordance with claim 9, wherein saidenclosure includes a top cover which is torispherical and a body whichis a pressurized vessel.
 11. A modular multi-stack fuel cell assembly inaccordance with claim 9, in which: said base section includes: a supportring having an upper part which supports said enclosure and a lowerpart; and a structural base attached to said bottom part of said supportring and which supports said fuel cell stacks.
 12. A modular multi-stackfuel cell assembly in accordance with claim 11, in which: said basesection further includes a floor extending over the extent of said upperportion of said ring and thermally insulating the space within said ringbelow said upper portion from the interior of said enclosure.
 13. Amodular multi-stack fuel cell assembly in accordance with claim 12, inwhich: the part of said ring between said upper portion and said lowerportion includes areas for penetration into said enclosure.
 14. Amodular multi-stack fuel cell assembly in accordance with claim 13, inwhich: the part of said ring between said upper portion and said lowerportion includes all the areas for penetration of instrumentation,electrical and process control into said enclosure.
 15. A modularmulti-stack fuel cell assembly in accordance with claim 12, in which:said floor has apertures therethrough for passage of said fuel cellstacks supported by said structural base.
 16. A modular multi-stack fuelcell assembly in accordance with claim 15, in which: said structuralbase includes a plurality beams forming a grill pattern defining asupport frame for each of said fuel cell stacks.
 17. A modularmulti-stack fuel cell assembly in accordance with claim 16, in which:said floor has an aperture for passage of said gas distributor; and saidgrill pattern defines a central area for providing support for said gasdistributor.
 18. A modular multi-stack fuel cell assembly in accordancewith claim 17, in which: the support frames defined by said grillpattern are symmetrically situated with respect to the central areadefined by said grill pattern.
 19. A modular multi-stack fuel cellassembly in accordance with claim 9, wherein: each of said stacks hasfirst and second opposing faces for receiving fuel gas and expellingexhausted fuel gas, respectively, and third and fourth opposing facesfor receiving oxidant gas and expelling exhausted oxidant gas,respectively and first, second and third manifolds abutting said first,second and fourth faces; and said containment structure serves as amanifold for each of said fuel cell stacks receiving oxidant gas.
 20. Amodular multi-stack fuel cell assembly in accordance with claim 19,wherein: each of said fuel cell stacks includes first and second endplates; and said gas distributor distributes fuel to and receivesexhausted fuel and oxidant gases from each of said fuel cell stacksthrough the end plates of the fuel cell.
 21. A modular multi-stack fuelcell assembly in accordance with claim 9, further comprising: thermalinsulation disposed on the inner wall of said enclosure.
 22. A modularmulti-stack fuel cell assembly in accordance with claim 21, wherein:said thermal insulation includes a plurality of thermal insulationlayers, each of said thermal insulation layers comprising abuttingsegments, the positions at which the segments of each thermal insulationlayer abut being offset from layer to layer.
 23. A modular multi-stackfuel cell assembly in accordance with claim 22, further comprising: pinsand clips for joining said thermal insulation layers together and to theinner wall of said enclosure.
 24. A modular multi-stack fuel cellassembly in accordance with claim 22, further comprising: a condensationaccumulation layer followed by a hydrophobic layer situated between saidthermal insulation and the inner wall of said enclosure.
 25. A modularmulti-stack fuel cell assembly in accordance with claim 22, furthercomprising: a stainless steel lining disposed on the surface of saidinsulation farthest from said inner wall of said enclosure.
 26. Amodular multi-stack fuel cell assembly in accordance with claim 9,wherein: said enclosure includes a plurality of ports for receivingpiping, each of said ports having a stepped configuration.
 27. A modularmulti-stack fuel cell assembly in accordance with claim 26, furthercomprising: thermal insulation disposed within portions of the innerareas of said ports.
 28. A modular multi-stack fuel cell assembly inaccordance with claim 26, wherein: said plurality of ports includesfirst and second ports for receiving fuel and oxidant gas, respectively,and third and fourth ports for exhausting exhausted fuel and oxidantgas, respectively.
 29. A modular multi-stack fuel cell assembly inaccordance with claim 28, wherein: said ports are aligned along a firstdirection.
 30. A modular multi-stack fuel cell assembly in accordancewith claim 29, wherein: said gas distributor includes first, second andthird sections, said first section for distributing received fuel toeach of said fuel cell stacks, said second section for receivingexhausted fuel gas from each of said fuel cell stacks and said thirdsection for receiving exhausted oxidant gas from each of said fuel cellstacks; and said first, second and third sections of said distributorare aligned along a second direction.
 31. A modular multi-stack fuelcell assembly in accordance with claim 30, wherein: said seconddirection is parallel to said first direction.
 32. A modular multi-stackfuel cell assembly in accordance with claim 31, wherein: said first andsecond directions are in the vertical direction.
 33. An end plateassembly for a fuel cell stack which is supplied oxidant gas and fueland which generates fuel exhaust gas and oxidant exhaust gas, the endplate assembly having an inlet area adapted to receive an exhaust gas,an outlet area and a passage connecting said inlet area adapted to carryexhaust gas received at said inlet area from said inlet area to saidoutlet area.
 34. An end plate assembly in accordance with claim 33,wherein: said end plate assembly comprises a hollow body having upperand lower walls and a number of side walls connecting the upper andlower walls.
 35. An end plate assembly in accordance with claim 34,wherein: said inlet area is in a first side wall of said hollow body andsaid outlet area is in a second side wall of said hollow body, and saidpassage is defined by the interior of said body.
 36. An end plateassembly in accordance with claim 34, wherein: said first side wall ofsaid hollow body has areas adapted to engage seals of a manifold of saidfuel cell stack.
 37. An end plate assembly in accordance with claim 35,further comprising: support members connecting said upper and lowerwalls of said hollow body for strengthening said end plate assembly. 38.An end plate assembly in accordance with claim 37, wherein: said supportmembers are further configured to control the flow of the exhaust gasthrough said passage.
 39. An end plate assembly in accordance with claim37, wherein: said support members are posts.
 40. An end plate assemblyin accordance with claim 37, wherein: the received exhaust gas isoxidant exhaust gas.
 41. An end plate assembly in accordance with claim40, further comprising: a terminal affixed to said upper wall adapted tofunction as an electrical output terminal for said stack.
 42. An endplate assembly in accordance with claim 41, wherein: said first andsecond side walls of said hollow body oppose one another.
 43. An endplate assembly in accordance with claim 42, wherein: said hollow bodyhas a rectangular shape.
 44. An end plate assembly in accordance withclaim 35, wherein: said exhaust gas is fuel exhaust gas.
 45. An endplate assembly in accordance with claim 44, wherein: said end plateassembly has a further inlet area adapted to receive fuel, a furtheroutlet area and a further passage connecting said further inlet area andfurther outlet area adapted to carry fuel received at said further inletarea from said further inlet area to said further outlet area.
 46. Anend plate assembly in accordance with claim 45, wherein: said furtherinlet area is in said second side wall of said hollow body, and saidfurther outlet is in a third side wall of said hollow body.
 47. An endplate assembly in accordance with claim 46, further comprising: aterminal affixed to said lower wall adapted to function as an electricaloutput terminal for said stack.
 48. An end plate assembly in accordancewith claim 47, wherein: first and third side walls of said hollow bodyoppose one another.
 49. An end plate assembly in accordance with claim48, wherein: said hollow body has a rectangular shape.
 50. A containmentstructure for enclosing fuel-cell stacks, said containment structurehaving a base section for supporting the fuel cell stacks inpredetermined positions and an enclosure engaging the base member forenclosing the fuel-cell stacks, said base section including a supportring having an upper part which supports said enclosure and a lowerpart, a structural base attached to said lower part of said support ringwhich supports said fuel-cell stacks and a floor extending over theextent of said upper part of said ring and thermally insulating thespace within said ring below said upper part from the interior of saidenclosure.
 51. A containment structure in accordance with claim 50,wherein said enclosure includes a top cover which is torispherical and abody which is a pressurized vessel.
 52. A containment structure inaccordance with claim 51, in which: the portion of said ring betweensaid upper part and said lower part includes areas for penetration intosaid enclosure.
 53. A containment structure in accordance with claim 52,in which: the portion of said ring between said upper part and saidlower part includes all the areas for penetration of electrical controlinto said enclosure.
 54. A containment structure in accordance withclaim 50, in which: said floor has apertures therethrough for passage ofthe fuel-cell stacks to be supported by said structural base.
 55. Acontainment structure in accordance with claim 54, in which: said floorhas drains for passage of collected water from internally formedcondensation.
 56. A containment structure in accordance with claim 50,in which; said structural base includes a plurality beams forming agrill pattern defining a support frame for each of said fuel cellstacks.
 57. A containment structure in accordance with claim 54, inwhich: said floor has an aperture for passage of a gas distributor; andsaid grill pattern defines a central area for providing support for saidgas distributor.
 58. A containment structure in accordance with claim57, in which: the support frames defined by said grill pattern aresymmetrically situated with respect to the central area defined by saidgrill pattern.
 59. A containment structure for enclosing fuel cellstacks, said containment structure having a base section for supportingthe fuel cell stacks in predetermined positions, an enclosure engagingthe base member for enclosing the fuel cell stacks and thermalinsulation disposed on the inner wall of said enclosure.
 60. Acontainment structure in accordance with claim 59, wherein: said thermalinsulation includes a plurality of thermal insulation layers, each ofsaid thermal insulation layers comprising abutting segments, thepositions at which the segments of each thermal insulation layer abutbeing offset from layer to layer.
 61. A containment structure inaccordance with claim 60, further comprising: pins and clips for joiningsaid thermal insulation layers together and to the inner wall of saidenclosure.
 62. A containment structure in accordance with claim 60,further comprising: a condensation accumulation layer followed by ahydrophobic layer situated between said thermal insulation and the innerwall of said enclosure.
 63. A containment structure in accordance withclaim 62, further comprising; a stainless steel lining disposed on thesurface of said thermal insulation farthest from said inner wall of saidenclosure.
 64. A fuel cell assembly comprising: a plurality of fuelcells arranged in a stack; an end plate assembly abutting the fuel cellat an end of said stack, said end plate assembly having an inlet areaadapted to receive an exhaust gas from said stack, an outlet area and apassage connecting said inlet area and outlet area and adapted to carrysaid exhaust gas received at said inlet area from said inlet area tosaid outlet area.
 65. A fuel cell stack in accordance with claim 64,further comprising: a further end plate assembly abutting the fuel cellat a further end of said stack opposing said end, said further end plateassembly having an further inlet area adapted to receive a furtherexhaust gas from said stack, a further outlet area and a further passageconnecting said further inlet area and further outlet area and adaptedto carry said further exhaust gas received at said further inlet areafrom said further inlet area to said further outlet area.
 66. A fuelcell stack in accordance with claim 65, wherein: said exhaust gas isoxidant exhaust gas and said further exhaust gas is fuel exhaust gas.67. A fuel cell stack in accordance with claim 66, wherein: said furtherend plate assembly has another inlet area adapted to receive fuel,another outlet and another passage connecting said another inlet areaand another outlet area and adapted to carry fuel received at saidanother inlet area from said another inlet area to said another outletarea.
 68. A fuel cell stack in accordance with claim 67, wherein: saidstack has first and second opposing faces for receiving fuel gas andexpelling exhausted fuel gas, respectively, and third and fourthopposing faces for receiving oxidant gas and expelling exhausted oxidantgas, respectively and said fuel cell stack assembly further comprises:first, second and third manifolds abutting said first, second and fourthfaces; and wherein said third manifold communicates with said inlet areaof said end plate assembly, said first manifold communicates with saidanother outlet area of said further end plate assembly, and said secondmanifold communicates with further inlet area of said further manifoldassembly.
 69. A fuel cell stack in accordance with claim 68, wherein:said third manifold overlaps with said inlet area of said end plateassembly, said first manifold overlaps with said another outlet area ofsaid further end plate assembly, and said second manifold overlaps withfurther inlet area of said further manifold assembly.